Long before human civilization existed, a massive asteroid weighing 18.4 billion tons
was on an imminent collision course with Earth, having already partially broken up as it approached
the planet.
Moments later, a massive fireball became visible which shined 125 times brighter than the sun,
being visible for several thousand miles.
Then, a powerful explosion occurred, quickly carving a 4.5 mile deep crater.
This flung up large amounts of rock which then reentered the atmosphere as superheated
material, going on to start wildfires around large swaths of the northern hemisphere.
What had just occurred was the formation of the Hiawatha Impact Crater in Greenland.
Yet, unlike what the animation just showed, this impact event did not occur when Greenland
was heavily glaciated, or even glaciated at all.
Despite being the 25th largest confirmed impact crater on Earth, Hiawatha Crater was only
discovered in 2018.
This crater is located in far northwestern Greenland, where it is 159 kilometers northeast
of the small town of Qaanaaq.
Zooming in, you can already see a suspiciously circular outline on the crater's western and
northern sides.
With this being said, this very large impact structure remained undiscovered for a lengthy
period of time because it was and still is buried underneath a kilometer or a little
more than 3,280 feet thick of ice.
It was only during the late 2000s that deep ground penetrating radar became accessible
that the ability to discover this crater through overflying it with an equipped aircraft became
possible.
Although Hiawatha Crater used to be much deeper, it now measures a mere 320 meters or 1050
feet deep.
And, Hiawatha Crater measures 31 kilometers or 19.3 miles wide, meaning that you could
easily fit all of Washington D.C. or even Paris inside it.
It is truly a massive crater, whose age remained a mystery until quite recently.
If you were to remove all of Greenland's ice, you would find a series of Precambrian rocks,
many over 1 or 2 billion years old, which cover much of the region.
In the region where Hiawatha Crater is located, the impact site was underlain by 1.7 billion
year old igneous and metamorphic rocks.
However, since the crater was overlaid by a kilometer of ice, the oldest of which formed
in the pleistocene period, the crater must therefor date between sometime in the Pleistocene
period and 1.7 billion years ago.
Well, after a well done study which analyzed zircons to determine an age, the Hiawatha
Crater was dated to 57.99 million years old.
This occurred during a time period when Earth was much hotter than it is today, with average
temperatures being 8 degrees Celsius or 14.4 degrees Fahrenheit warmer than it is today.
Greenland at the time actually lived up to its name, as it contained a fairly cold but
also lush densely forested climate which actually was green!
On the southwest and eastern section of the country, large flood basalt eruptions were
ongoing, outputting thousands of cubic kilometers of lava in as little as only a few decades.
You might note that the age of Hiawatha Crater is somewhat close to a sudden worldwide spike
in temperature known as the Paleocene Eocene Thermal Maximum when temperatures spiked by
another 6 degrees Celsius.
Yet, that was primarily caused by the flood basalts around 56 million years ago, with
this Hiawatha Crater impact and its half a million year margin of error having occurred
too early to have produced this climatic anomaly.``
The asteroid which would go on to form Hiawatha Crater likely originated in the asteroid belt
between Mars and Jupiter, where it represented a fragment of a differentiated asteroid core,
meaning it was primarily composed of iron and thus was quite dense, being essentially
the density of the lead ore known as galena.
The asteroid which measured 1,675 meters or 5,495 feet wide was eventually dislodged from
its stable orbit, and began its new orbital path which would lead it into a collision
with Earth.
It advanced at a speed of 17 kilometer per second or 38,000 miles per hour until it began
burning up in Earth's atmosphere.
Seconds later, it impacted the lush forests of Greenland, generating an explosion equivalent
in energy to the detonation of 637,500 megatons of TNT.
Due to the intense thermal radiation generated by the blast, everything organic within a
400 kilometer radius ignited.
As a magnitude 8.5 earthquake was generated, a more than 10,000 mile per hour shockwave
raced outwards in all directions.
This would go on to flatten all trees facing outwards from the blast to a distance of 500
kilometers.
Although a short term impact winter may have occurred, lasting around 7 years and resulting
in 10 degrees Celsius of cooling over that time period, it did not cause a major extinction
event or have long term climatic implications on the planet.
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